Sensor Patent Dispute Revived-in-Part Due to Improper Claim Construction

In SSI Technologies, LLC v. Dongguan Zhengyang Electronic Mechanical Ltd., No. 21-2345 (Fed. Cir. Feb. 13, 2023), the Federal Circuit affirmed-in-part, reversed-in-part, vacated-in-part, and remanded a district court decision granting summary judgment of non-infringement and invalidity.

SSI Technologies (“SSI”) brought suit against Dongguan Zhengyang Electronic Mechanical (“DZEM”) for infringement of two patents directed to sensors for determining the characteristics of fluid in a container.  With respect to the first patent, U.S. Patent No. 8,733,153, the dispute focused on the construction of the item (b) in the following Markush group: “a) whether a measured volume is out of range and b) a dilution of the fluid is detected while the measured volume of the fluid decreases.” The district court construed item (b) to require the consideration of the measured volume of the fluid. With respect to the second patent, U.S. Patent No. 9,535,038, the district court construed the term “filter” to require a “porous structure” with a certain size opening. Based on these constructions, the district court granted summary judgment of non-infringement.

The Federal Circuit affirmed the district court’s claim construction for the ’153 patent, finding no error in its analysis. The Court first explained that the ’153 patent discloses two types of errors that the claimed system is designed to detect, which correspond closely to the two items in the Markush group added to the claim during prosecution. The Court found that this “parallelism” supported the district court’s construction.  The Federal Circuit reversed the district court’s claim construction for the ’038 patent. The Court found that there was no support for this construction, because the term “porous” does not appear in the specification nor is there any requirement in the specification regarding the size of the filter openings. The Court thus adopted SSI’s proposed construction and vacated the district court’s decision granting summary judgment of non-infringement.